Study On Autotoxicity Of Eight Invasive And Native Plants

Allelopathy is a common biological phenomenon;almost all organisms can produce allelopathic substances to affect the growth and development of other organisms.Phytoallelopathy is a chemical interaction between a donor plant and a recipient plant,which can have either positive or negative effects.The harmful effects of the allelochemicals from a given plant species on the same species are also known as autotoxicity.To assess the roles of autotoxicity in exotic plant invasions,its effects on abundance of native plants in the fields,and the possibility of using autotoxic substances to control exotic and native harmful plants,four invasive alien plants(Ambrosia trifida,Xanthium strumarium,Amaranthus retroflexus and Abutilon theophrasti)and four native plants(Humulus scandens,Commelina communis,Metaplexis japonica and Viola philippica)were used as materials to study the effects of different concentrations of leaf aqueous extracts on the cell membrane permeability and seed germination of the same species.The main conclusions are as follows:The leaf aqueous extracts of the eight plant species significantly increased the relative conductivity of the extravasation liquid of their own leaves,i.e.,leaf cell membranes were damaged siginificantly,showing autotoxic effects for the eight plant species.The higher the treatment concentration of the leaf extract,the higher the relative conductivity of the leaf extravasation liquid.The leaf contents of hydrogen peroxide and superoxide anion free radicals were also increased significantly by the treatments with the leaf aqueous extracts in A.theophrasti,H.scandens and C.communis.The higher the leaf extract concentration,the higher the two reactive oxygen species.At low concentration(0.5%),leaf aqueous extracts significantly promoted the germination rates of their own seeds;at intermediate(1.0%)and high(2.0%)concentrations,leaf aqueous extracts significantly inhibited the germination rates of their own seeds.In our experiment,seed germination rates were not significantly affected by the leaf aqueous extracts in some species,which may be due to the low concentrations of the extracts(< 2.0%).Integrating the effects of the leaf aqueous extracts on both the cell membrane permeability and seed germination,we found that the autotoxic effects of the leaf extracts differed greatly among the eight species.The autotoxic effects were weaker in the four invasive plants A.trifida,A.theophrasti,X.strumarium and A.retroflexus,while stronger in the four native plants H.scandens,C.communis,M.japonica and V.philippica.The low autotoxicity may be beneficial to the seed germination of the invasive plants such as A.trifida,X.strumarium,A.retroflexus and A.theophrasti,and therefore to the formation of a monidominant plant community.The low autotoxicity is also beneficial to maintainance of the integrity of leaf cell membranes and normal physiological activities,promoting plant growth and development.Thus,the low autotoxicity may be one of the mechanisms underlying invasion success of these invasive plants.However,the strong autotoxicity may not influence the abundance of the native plants such as H.scandens and C.communis.Autotoxicity may not be used to control these invasive alien plants;but has the potential for controlling common native weeds.